1. Field of the Invention
The present invention relates generally to tamper-indicating closures for containers, and more particularly to a tamper-evident plastic closure including a pilfer band having a vertical weakened region formed by a vertical line of reduced thickness which is formed by cutting or scoring.
2. Description of the Related Art
Tamper-indicating or tamper-evident container closures are well-known. For example, copending U.S. patent application Ser. No. 09/016,266, filed on Jan. 30, 1998, which is hereby incorporated by reference in its entirety, discloses tamper evident plastic closures for use in connection with bottles or like containers having a threaded neck and a locking ring. The tamper evident function is there provided by a pilfer band which is initially attached to the closure cap via a circumferential score line, but which breaks or separates from the closure cap and remains on the bottle when the closure cap is unscrewed or otherwise removed from the bottle for the first time. The pilfer band includes tabs or projections which engage the threads or locking ring of the bottle so as to resist the removal of the pilfer band.
It is also known to provide the pilfer band with a vertical line of reduced thickness which may be molded or cut into the plastic closure, hereinafter referred to as a vertical break line. The presence of the vertical break line results in a preferential rupture of the pilfer band at the vertical break line due to hoop stresses when the closure cap is first removed from the bottle, so that the pilfer band breaks and does not fully separate from the closure cap when the closure cap is first removed from the bottle. This is shown in U.S. Pat. Nos. 5,257,705; 3,329,295; 3,601,273; 4,418,828; 5,660,289 and 4,666,053. The pilfer band therefore remains with the closure cap, which is desirable for use with returnable bottles.
As a practical matter, it has proven difficult to produce such closure caps on a commercial basis such that the vertical break lines will reliably rupture during removal of the cap from the bottle. In the case of cut or scored vertical break lines, this is due in part to the difficulty of accurately controlling the depth of cut of the vertical break line adjacent the bottom edge of the pilfer band.